var grades = {
    showSubtab:function(tabId) {
	var c = document.getElementsByClassName('sub-tab').length;
	for (var i = 0;i < c;i++) 
	    {
		document.getElementsByClassName('sub-tab')[i].style.display = 'none';
	    }
	document.getElementById(tabId).style.display = 'block';
    },
    makeRequest:function(url)
    {
        var httpRequest;
	url = "/products/dothemath/tabcontent/" + url + ".htm";
	
        if (window.XMLHttpRequest) { // Mozilla, Safari, ...
            httpRequest = new XMLHttpRequest();
            if (httpRequest.overrideMimeType) {
                httpRequest.overrideMimeType('text/html');                
            }
        } else if (window.ActiveXObject) { // IE
            try {
                httpRequest = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (e) {
                try {
                    httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (e) {}
            }
        }

        if (!httpRequest) {
            alert('Giving up :( Cannot create an XMLHTTP instance');
            return false;
        }
        httpRequest.onreadystatechange = function() { grades.displayNewGrade(httpRequest); };
	//alert(url);
        httpRequest.open('GET', url, true);
        httpRequest.send(null);
    },
    alertContents:function(httpRequest)
    {
        if (httpRequest.readyState == 4) {
            if (httpRequest.status == 200) {
                alert(httpRequest.responseText);
            } else {
                alert('There was a problem with the request.');
            }
        }
	
    },
    displayNewGrade:function(httpRequest)
    {
	if (httpRequest.readyState == 4) {
            if (httpRequest.status == 200) {
                var obj = document.getElementById("is");
		obj.innerHTML = httpRequest.responseText;	
            } else {
                //
            }
        }		
    }
}